Friday 4 November 2011 14.38 EDT
First published on Friday 4 November 2011 14.38 EDT

Iran faced mounting pressure over its nuclear ambitions when France and China made separate pleas to Tehran ahead of a crucial report next week.

The French president Nicolas Sarkozy on Friday condemned Iran's "obsession" with developing nuclear capability, and said any attempt to engineer atomic weapons was a clear violation of all international rules. Though he appeared to rule out any imminent military campaign, he said France would be prepared to act if Israel was under threat. "France will not stand by with arms crossed," he said.

China also urged the Iranians to be less confrontational and said the regime needed to co-operate fully with the International Atomic Energy Authority (IAEA), which is due to publish its latest bulletin on the republic's nuclear ambitions next week. It was time for Iran to show flexibility and sincerity, an official said.

Tehran, however, stepped up its rhetoric as the perceived hypocrisy from the US caused anger.

At a rally to mark the anniversary of the 1979 seizure of the US embassy in Tehran, tens of thousands of protesters heard Iran's senior nuclear negotiator, Saeed Jalili, accuse Washington of waging terrorism against the country.

As demonstrators chanted "Death to the USA", Jalili said a dossier of alleged crimes would be presented to the UN, and that it included assassination plots. Three Iranian nuclear scientists have been shot in recent years, the most recent in July.

Tehran says the killings were instigated by the US and Israel, and that the scientists were targeted because they were on a list of nuclear experts identified in sanctions brought against the regime.

"This question still remains … why people on the US sanctions list are assassinated in Iran," said Jalili. "What relationship exists between assassinations and US sanctions other than terrorists being directed by the US?

"The US is employing terrorism to promote its objectives ... we will sue the United States. The UN needs to take the necessary measures to prosecute and punish the US government for directing terrorist activities [against Iran]."

According to Fars, the semi-official news agency, protesters held a poster of President Barack Obama which read "wanted, dead or alive" and "Obama terrorist".

Another said that developing a nuclear programme was Iran's absolute right.

The crowd also showed its support for the Quds Force, the elite unit of Iran's Revolutionary Guard. The US has accused the Quds of masterminding terrorism abroad, including the attempt to kill the Saudi ambassador to Washington exposed last month. Iran has denied involvement in the plot and insisted that it is not intending to develop nuclear weapons. Tehran says it is only interested in developing atomic energy for civilian purposes.

The IAEA has written a number of reportschallenging these claims, and the next one is thought to contain the most authoritative detail yet casting doubt on Tehran's assurances.

It is estimated that Iran already has enough weapons-grade uranium to make up to four weapons. Western diplomats are increasingly concerned that the regime is hiding some of its centrifuges, which enrich uranium ore, inside the fortified military base at Qom – which may be beyond the reach of missile attacks.

The US has led efforts to put pressure on Iran through sanctions, but the White House has apparently backed away from introducing further, potentially crippling restrictions because of fears it would destabilise oil markets when the global economy is teetering on the brink. The Los Angeles Times said the weakness of the American economy had made Obama think twice.

However, a senior US security official, quoted anonymously by Reuters, made it clear that the administration regards Iran as its prime concern. "The biggest threat to the US and to our interests and to our friends, I might add, has come into focus and it's Iran," said the official, who was speaking at a forum in Washington. He said he did not believe Iran wanted to provoke a conflict and added that he did not know whether the Islamic state had decided to build a nuclear weapon.

Beijing's intervention is potentially significant – it has repeatedly urged the IAEA to be patient with Iran. But Chinese foreign ministry spokesman Hong Lei made clear that Tehran needed to co-operate with the nuclear watchdog.

"The IAEA should adopt an impartial and objective stance and seek positive co-operation with Iran to clarify certain questions," he said. "Iran should also show flexibility and sincerity and have earnest co-operation with the IAEA. China opposes the use of force or the threat of the use of force in international affairs. At present, avoiding any new upheaval in the Middle East is extremely important."